RB1 - has ran the football 203 times for an average of 4.1 over his career. He is averaging 4.4 for this season. He has a rushing TD every 51 attempts, 4 total on his career.
RB2 - has ran the football 265 times for an average of 5.1 over his career. He is averaging 5.1 for this season. He has a rushing TD every 33 attempts, 8 total on his career.
No need to dilute it to 4 attempts, a particular down, or a harvest moon.
Both RBs have value to this team. And both need to get the football plenty.
But If I'm valuing one above the other Im taking the guy that gets you further down the field per attempt and scores more frequently. Thatd be RB2 (or Chandler)